1. Field of the Invention
The present invention is directed to a stock material supplied on a roll from which lengths may be cut and used in circulation air systems to span the spaced opposed edges of adjacent air ducts to prevent leakage of air and transmission of vibration from one duct to another.
2. The Prior Art
It is known in circulating air systems, such as air conditioning systems, air heating systems and the like to avoid the transmission of vibrations, for instance from a blower duct section to a distributor duct section, to provide in spanning relation between the noted section a joint comprised of metallic margins having an air-impervious flexible material bonded therebetween. The metal margins are bent to the shape of the duct ends to be connected, and are secured to such ends, the flexible material interposed between the margins minimizing transmission of vibration while at the same time preventing air leakage. Contemporary air circulating systems typically are insulated so as to make the same as energy efficient as possible.
U.S. Pat. No. 4,183,577, assigned to the assignee hereof, discloses a highly efficient form of flexible connector which, in addition to providing vibration damping, also functions to minimize heat loss at the interface between adjacent duct ends.
The material of the above referenced patent comprises a flattened tubular material spanning the metallic members connected to the ducts, the tubular material encompassing therein a thickness of insulating material or stuffing.
Heretofore the materials employed as insulation have been flexible foams, such as urethane foams and/or rubber foams, or batts of material such as glass wool.
It has been observed that the use of foams, while providing highly efficient initial insulating properties, have over time lost their insulating effect. This loss is due to the tendency of such foam materials to harden and crumble due to repeated billowing and contracting effects which result from repeated cycles of compression and relaxation as the air systems are pressured and turned off.
A further factor which results in breakdown of the material is the exposure of the insulation to high heats when used in the winter and to the cooling influences when used in air conditioning systems.
The use of glass wool batts has been found to provide superior results since such batts are less susceptible to the degrading effects of the heating and cooling and breakdown under repeated cycles of billowing and relaxation.
However, it has been found that in use for protracted periods glass wool has tended to lose its shape or configuration as a band extending between the metallic margins and has taken the form of a generally cylindrical mass which progressively compacts under repeated cycling, with the result that areas form between the confining flexible layers which are free of insulation, with resultant degradation of the insulating properties.